Incremental length gauge for high precision use in harsh environments

Called SPECTO ST 3087RC, the unit has a special housing to protect its precision mechanism. A built-in spring keeps the plunger, surrounded by a rubber bellows, retracted behind a guard and splash cap when the gauge is in its rest position. Extension of the plunger to the measuring position is actuated by compressed air, normally with the coolant switched off.

A significant increase in productivity and a reduction in floor-to-floor time result from not having to transfer components to a measuring station external to the machine tool, or to a quality control department. Should rework be necessary after metrology functions have been completed, in-process gauging preserves accuracy by eliminating the need to set the component up again for a second operation.

High accuracy positional values over the full stroke of the gauge allow diverse components to be measured from the same fixture. Internal photoelectric scanning of plunger position by means of a DIADUR scale grating with a 20μm period, together with the use of an especially durable ball-bush guide, permit consistent repeatability of probing even when measuring oblique or curved surfaces.

The ST 3087 RC has an IP rating of 67, so it is totally protected against ingress of dust and is unaffected by high pressure coolant jets and even short periods of immersion. It is also tolerant to extremes of temperature, vibration and shock. The 1 VPP interface opens up many possibilities for feedback to a machine tool control, as well as for logging measured results and processing them for statistical analysis.